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Emery, orcorundite, is a dark granular rock used to make an abrasive powder. The rock largely consists ofcorundum (aluminium oxide), mixed with other minerals. Industrial emery may contain a variety of other minerals and synthetic compounds. Crushed or naturally eroded emery (known asblack sand) is used as anabrasive. Turkey and Greece are the main suppliers of the world's emery.
Emery is a granular rock used to make an abrasive powder. It largely consists ofcorundum (aluminium oxide), mixed with other minerals such as the iron-bearingspinels,hercynite, andmagnetite, and alsorutile (titania). Industrial emery may contain a variety of other minerals and synthetic compounds such asmagnesia,mullite, andsilica.
Emery is black or dark grey in colour, less dense than translucent-brown corundum with aspecific gravity of between 3.5 and 3.8. Because it can be a mixture of minerals, no definiteMohs hardness can be assigned: the hardness of corundum is 9 and that of some spinel-group minerals is near 8, but the hardness of others such as magnetite is near 6.
Crushed or naturally eroded emery (known asblack sand) is used as anabrasive—for example, onemery boards andemery cloth. It is also used as a traction enhancer inasphalt andtarmac mixtures.
A small quantity of emery is used in coated abrasive products, but its main use in theUnited States is wear-resistant floors and pavements.[1] Many tons are shipped to Asia to be used in grinding rice.[2]
Solomon's shamir, a substance used to cut stone during construction of theFirst Temple, was likely emery.[3]
Turkey and Greece are the main suppliers of the world's emery. These two countries produced about 17,500 tons of the mineral in 1987.[4]
The Greek island ofNaxos used to be the main source of this industrially important rock type. It has been mined on the eastern side of Naxos for well over two thousand years as mentioned byPliny the Elder'sThe Natural History, book XXXVII, chp. 32. However, demand for emery has decreased with the development ofsintered carbide and oxide materials as abrasives.
In the United States, theOccupational Safety and Health Administration has set permissible exposure limits for emery in the workplace:TWA 15 mg/m3 total exposure and TWA 5 mg/m3 respiratory exposure.[5]
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